This invention relates to a pipe coupling for a female screw which has a male screw to be connected to a female screw port formed in a fluid pressure device.
Japanese Patent No. 2758380, for example, discloses a pipe coupling for a female screw which has a male screw to be connected to a female screw port formed in a fluid pressure device. FIGS. 8 and 9 show the basic structure of the pipe coupling disclosed in the patent. FIG. 8 is a sectional view of the pipe coupling, showing its non-connected state, and FIG. 9 is an enlarged view of a section A incorporated in the pipe coupling. In the following description, the words xe2x80x9cforward (front)xe2x80x9d and xe2x80x9crearward (rear)xe2x80x9d mean the right-hand direction and the left-hand direction in FIG. 8, respectively.
As shown, the pipe coupling for a female screw disclosed in the patent comprises a cylindrical body 100, arm members 103 provided at the front end of the body 100, and a sliding rod 104 fitted in the body 100. The cylindrical body 100 includes a front cylinder 101 and a rear cylinder 102. The front and rear cylinders 101 and 102 are connected to each other by screwing a male screw provided on the outer peripheral surface of a front end portion of the rear cylinder 102, into a female screw formed in the inner peripheral surface of a rear end portion of the front cylinder 101. Further, a connecting cylinder 105 is fitted on a connecting section of the front and rear cylinders 101 and 102. A cylindrical stepped arm base 106 is engaged with the inner peripheral surface of the front cylinder 101. The arm members 103 are supported by the front end of the arm base 106 so that they can swing about their respective support shafts 107. The arm members 103 are arranged to swing between an open position in which they are parallel to the longitudinal central axis of the cylindrical body 100, and a closed position in which they are inclined to the axis. The front end portions of the arm members 103 project forward (i.e. in the right-hand direction in the figure) from the front end of the front cylinder 101. Engagement portions (male screw portions) 108 are formed on the outer peripheral surfaces of front end portions of the arm members 103, so that they will be engaged with the female screw portion formed in the inner surface of a female screw port 115 in a fluid pressure device, when the arm members 103 are in the open position.
A cylindrical seal holder 109 is fitted in a front end portion of the front cylinder 101. An O-ring 110 is fitted on the outer peripheral surface of the seal holder 109, thereby airtightly sealing a clearance between the seal holder 109 and the front cylinder 101. A seal ring 111 is fitted in a front end portion of the seal holder 109. The rear end of the seal holder 109 is slidably inserted between the inner peripheral surface of the front cylinder 101 and the outer peripheral surface of the arm base 106. The seal holder 109 is always urged in the right-hand direction in the figure by a spring 112 located between itself and the arm members 103. As a result, the seal ring 111 is also urged in the right-hand direction in the figure.
In the open position, the opposed inner surfaces of the arm members 103 are parallel to each other. At this time, the distance between the opposed inner surfaces of the arm members 103 is substantially the same as the outer diameter of a lock pin 113, described later, incorporated in the sliding rod 104. On the other hand, in the closed position, the distal ends of the arm members 103 contact each other and the diameter of the contact portion of the male screw portions 108 is small, as is shown in FIG. 8.
When the lock pin 113 is inserted between the arm members 103, the outer peripheral surface of the lock pin 113 is engaged with the inner surfaces of the arm members 103, thereby outwardly opening the arm members 103 and keeping them in the open position.
The operation of connecting the pipe coupling constructed as above to a port in a fluid device will be described with reference to FIGS. 8 and 9. First, in the state shown in FIG. 8, the distal ends of the arm members 103 are inserted into the female screw port 115 of the fluid device, thereby further forwarding the pipe coupling and pushing the seal holder 109 into the front cylinder 101 against the urging force of the spring 112 with the seal ring 111 at the seal holder 109 side kept in contact with the fluid device. After that, the pressing surface 116 of the sliding rod 104, which constitutes the rear end of the rod, is pushed forward, thereby inserting the lock pin 113 between the arm members 103 and causing the arm members 103 to swing about the support shafts 107 and assume the open position. As a result, the male screw portions 108 formed of the front end portions of the arm members 103 are engaged with the female screw portion formed in the inner peripheral surface of the female screw port 115 of the fluid device. Further, in this state, the seal ring 111 is in contact with the end surface of the female port 115, thereby sealing a clearance between the pipe coupling and the fluid device, and also maintaining a state in which the pipe coupling is prevented from being disconnected from the fluid device.
When, in the connecting operation, the arm members 103 assume the open position about the support shafts 107, it is possible that the peaks of the thread of the male screw portions 108 of the arm members 103 will be aligned with the peaks of the thread of the female screw portion formed in the inner surface of the female screw port 115, and hence the male and female screws will not be engaged with each other. In this case, it is necessary to slightly move the pipe coupling forward or backward so as to shift the arm members 103 by half of one peak of the thread, in order to engage the screws with each other. When backwardly shifting the arm members 103 by half of one peak, with the rear end 109a of the seal holder 109 kept in contact with a stepped portion 101a formed in the inner peripheral surface of the front cylinder 101 as shown in FIG. 9, the seal holder 109 urged by the spring is shifted forward by half of one peak, and therefore the screws can be engaged with each other. However, when, in order to engage the screws, forward shifting the arm members 103 by half of one peak, and backward shifting the seal holder 109, urged by the spring, by half of one peak, the seal holder 109 cannot be shifted backward since the rear end 109a comes in contact with the stepped portion 101a. Accordingly, the arm members 103 cannot be shifted forward, which means that the screws cannot completely be engaged with each other (an unstable connecting state is established). If in this state, the screws are still tried to be engaged with each other, it is necessary to press the cylindrical body 100 by pressing the sliding rod 104 with an excessive force, or to press the cylindrical body 100 itself to thereby significantly deform the seal ring 111. This indicates a low operability of the pipe coupling, and may adversely affect the durability of the seal ring. Moreover, when, in order to engage the male screw 108 with the female screw formed in the inner surface of the port 115, the sliding rod 104 is inserted between the arm members 103 to open the arm members 103, and also the arm members are shifted backward by half of one peak so as to eliminate the defective engagement of the screws, in a state in which the spring 112 is not compressed (not warped), i.e. in a state in which the seal holder 109 is not pushed into the front cylinder 101 against the urging force of the spring 112, it is possible that the seal ring 111 of the seal holder 109 will be separated from the end face of the female screw port 115, thereby causing defective sealing.
It is a main object of the invention to provide a pipe coupling for a female screw, in which the state of engagement between a female screw portion formed in the inner peripheral surface of a female screw port incorporated in a fluid device, and male screw portions formed on distal end portions of arm members of the pipe coupling can be corrected by a natural and simple operation, and in which no excessive force is applied to a seal ring and hence the seal ring can have a long life.
It is another object of the invention to provide a pipe coupling for a female screw, which can reliably seal a female screw port incorporated in a fluid device to be connected, with a female screw portion, formed in the inner peripheral surface of the female screw port, correctly engaged with male screw portions formed on distal portions of arm members of the pipe coupling.
To attain the objects, there is provided a pipe coupling for a female screw to be connected to a female screw port formed in a fluid device, comprising: a cylindrical pipe coupling main body; a plurality of arm members contained in the pipe coupling main body and radially displaceable with respect to the pipe coupling main body, each of the arm members having a male screw portion provided on a distal end portion thereof and to be connected to the female screw port, the distal end portion projecting from an end of the pipe coupling main body to an outside thereof; a sliding member forward and backward slidably inserted in the pipe coupling main body, the sliding member shifting, by forward and backward movement thereof, the arm members between a closed position in which distal ends of the arm members contact each other, and an open position in which the distal ends of the arm members are separated from each other and the male screw portions of the distal end portions of the arm members can be engaged with the female screw port of the fluid device; a fluid passage formed in one of the sliding member and the pipe coupling main body and to be connected to a fluid passage formed in the fluid device when the male screw portions engage with the female screw port; a lock member provided in the pipe coupling main body for stopping movement of the sliding member such that the arm members are kept in the open position; a seal holder provided at an end of the pipe coupling main body and arranged to move forward and backward between an inner peripheral surface of the pipe coupling main body and outer peripheral surfaces of the arm members; a spring seat fitted on outer peripheral surface of the arm members such that it can move forward and backward; a spring interposed between the spring seat and the seal holder and urging the spring seat and the seal holder away from each other; a seal member provided on the seal holder and to be pressed against around the female screw port of the fluid device by an urging force of the spring to seal the female screw port; and a pressing member provided on the sliding member and to be brought into contact with the spring seat when the sliding member is moved in a direction in which the arm members are opened, thereby moving the spring seat so as to increase the urging force of the spring.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.